Regulation of the Translational Response to Cellular Stress

项目总结/摘要 基因表达的适当调节是确定和维持细胞身份以及 对细胞外环境的反应。在真核生物中，这需要一个多步骤的mRNA途径， 从转录到翻译并最终降解，细胞对变化条件的反应通常会诱导 在许多步骤中进行高度协调的变化。对不利压力条件的反应，如缺乏 营养素或氧化应激，在多种多样的生物体中通常是必需的，以确保细胞存活。 鉴于其大量的能量需求，蛋白质翻译的变化在细胞应激中起着特别关键的作用 反应，导致数千个基因的翻译改变。这种反应也变得失调， 一些疾病的病理学。值得注意的是，在应激过程中规避翻译调节的能力是 癌症进展的标志，促进细胞持续生长，改变应激反应， 翻译机制也会导致衰老。尽管存在这些疾病联系，但这些巨大的变化 翻译是规范的，并没有得到很好的理解。 Ded 1是一种保守的RNA解旋酶，在翻译起始中起关键作用。人类基因的改变 Ded 1的同源物DDX 3已在许多癌症中发现，包括小儿脑癌 髓母细胞瘤和自然杀伤/T细胞淋巴瘤。DDX 3的突变也与认知功能有关。 DDX 3与发育障碍有关，并且DDX 3参与包括HIV在内的几种病毒的复制。这些发现 强调了解Ded 1/DDX 3正常功能的重要性，因为这也可以揭示 与疾病相关的功能。在稳态条件下，Ded 1刺激翻译起始;然而， 最近的研究已经揭示Ded 1在应激条件下抑制翻译中具有主要作用， 特别是当细胞的中央营养传感器TOR通路失活时。该提案探讨了 Ded 1和相关因子在控制细胞应激的翻译反应中的功能。 具体来说，目的我将表征的压力功能Ded 1在响应TOR通路失活。 这一作用的机制，其中涉及重建和退化的关键翻译支架 因子eIF 4G，将被定义，和下游的后果，这一机制的翻译的具体 将测定mRNA。胁迫期间Ded 1和eIF 4G的上游调节因子和辅助因子将 也被识别和表征。目标II将检查Ded 1参与压力的另一部分 应激反应、应激颗粒的形成、mRNA和相关蛋白质的细胞质积累。它将 还测试了在含有Ded 1/DDX 3突变的细胞中是否影响应激反应， 髓母细胞瘤这项工作将大大提高我们对细胞翻译反应的理解， 并将告知未来的研究其在癌症和其他疾病中的失调。

PROJECT SUMMARY/ABSTRACT Proper regulation of gene expression is required for determining and maintaining cellular identity and for responding to the extracellular environment. In eukaryotes, this entails a multi-step pathway for mRNA from transcription to translation and eventual degradation, and cellular responses to changing conditions often induce highly coordinated changes in many of these steps. The response to adverse stress conditions, such as lack of nutrients or oxidative stress, is often necessary in a wide diversity of organisms in order to ensure cell survival. Given its large energy requirements, changes in protein translation play a particularly critical role in cellular stress responses, resulting in altered translation of thousands of genes. This response also becomes misregulated in the pathologies of a number of diseases. Notably, the ability to circumvent translation regulation during stress is a hallmark of cancer progression that promotes continued cell growth, and alterations to stress responses and the translation machinery also contribute to aging. Despite these disease links, how these massive changes to translation are regulated is not well understood. Ded1 is a conserved RNA helicase that plays critical roles in translation initiation. Alterations in the human homolog of Ded1, DDX3, have been found in a number of cancers, including the pediatric brain cancer medulloblastoma and natural killer/T-cell lymphoma. Mutations of DDX3 are also linked to a cognitive developmental disorder, and DDX3 is involved in replication of several viruses, including HIV. These findings underscore the importance of understanding the normal functioning of Ded1/DDX3 since this can also shed light on its disease-associated functioning. In steady-state conditions, Ded1 stimulates translation initiation; however, recent research has revealed that Ded1 has a major role in the repression of translation during stress conditions, specifically when the TOR pathway, the central nutrient-sensor of the cell, is inactivated. This proposal explores this function of Ded1 and associated factors in controlling the translational response to cellular stress. Specifically, Aim I will characterize the stress function of Ded1 in response to TOR pathway inactivation. The mechanism of this role, which involves remodeling and degradation of the critical translation scaffolding factor eIF4G, will be defined, and the downstream consequences of this mechanism on translation of specific mRNAs will be determined. Upstream regulators and accessory factors for Ded1 and eIF4G during stress will also be identified and characterized. Aim II will then examine Ded1 involvement in another part of the stress response, the formation of stress granules, cytoplasmic accumulations of mRNA and associated proteins. It will also test whether the stress response is affected in cells containing Ded1/DDX3 mutations associated with medulloblastoma. This work will greatly enhance our understanding of the translational response to cellular stress and will inform future studies of its misregulation in cancer and other diseases.